One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,4)(3,6,7,8)(9,10,15,18,13,19,14,20)(11,16,29,31,22,32,23,33)(12,24,28,35,26,17,27,36)(21,37,39,34,38,30,25,40)(2,4)(6,8)(9,11)(10,16)(12,25)(13,22)(14,29)(15,23)(17,34)(18,33)(19,32)(20,31)(21,27)(24,40)(26,39)(28,38)(30,35)(36,37) involution — undirected(1,3,5,7)(2,6,4,8)(9,12,13,26)(10,17,19,24)(11,21,22,38)(14,28,15,27)(16,30,32,37)(18,35,20,36)(23,39,29,25)(31,34,33,40)(1,4,5,2)(3,6,7,8)(10,18,19,20)(11,22)(12,26)(16,31,32,33)(17,35,24,36)(23,29)(27,28)(30,34,37,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.